In practice, semifinished products containing substantially no cocoa paste do not need particularly thorough conging, unlike other mixtures in which conging is normally essential to reduce the viscosity of the mixture, and especially to eliminate some of the volatile components of the cocoa paste and initiate chemical reactions to enhance the flavour of the semifinished product.
The conventional method currently used is discontinuous, and comprises loading the basic ingredients inside mixers consisting of tanks fitted inside with agitators. After a first mixing stage, the entire mixture is transferred to known cylinder-type pre-refining machines, and then to known, conveniently also cylinder-type, refining machines, which gradually reduce the mixture to the desired grain size, normally of less than 30 microns. The ground mixture is then transferred to conging machines known as conges, and, when the mixture in the conges reaches a given consistency, the other ingredients are added to make up the dosage, and the mixture is pumped into storage facilities, pending further processing. An example of such a system employing conging tanks is described, for example, in US Patent Application US 2007/0202241.
Though used for decades, the above method has various drawbacks. In particular, the refining process is discontinuous and slow, and involves bulky, high-cost machinery.
The conges normally used to process the semifinished product are also bulky and expensive, and the processing cycles are normally lengthy, to achieve a fluid enough product for further processing.
Conventional methods also pose problems when making production changeovers, which is a painstaking job, especially to clean the machinery.